NEW YORK (AP) — Deck the halls and man the battle stations. The fight has resumed.

I'm referring, of course, to the so-called War on Christmas, a yearly call to arms by those whose Christmas cheer is under siege. Or so they claim ... fear ... and warn.

This annual uproar may have escaped the notice of some Christmas observers.

Those are people who mean no disrespect to Christmas by replacing "Merry Christmas" with the more inclusive "Happy holidays." Those are people who are able to forgive as good intentions gone awry the occasional misguided stab at political correctness. ("Holiday tree"? Really?!)

Those are people who might be surprised to learn that Christmas is under threat of a power grab by atheists, libertines, elites, advocates for gay rights, pro-abortion rights and drug legalization, plus garden-variety left-wing wack jobs.

In short, those are people who aren't watching Bill O'Reilly.

No one is more vociferous in leading the Christmas pushback than this Fox News Channel superstar, whose seasonal war cry on "The O'Reilly Factor" has become a Christmas tradition of its own.

Every right-thinking person needs to "stand up and fight against this secular progressivism that wants to diminish the Christmas holiday," he fulminated recently to that night's guest, Fox News personality and former Arkansas governor Mike Huckabee. "We have to start to fight back against these people."

"You know, Bill," Huckabee said gently, "the nature of most Christians is not to get into a fight and a squabble."

"But you're gonna LOSE!" warned his host.

Turning the "No-Spin Zone" into a holiday war zone, O'Reilly is all for keeping Christ in Christmas.

At the same time, he proclaims that everyone — no matter their faith — should call a Christmas tree "a Christmas tree" and knock off their whining.

"No intelligent person could possibly see a secular display of Christmas as an imposition of religion," he declared. "A Christmas tree is a secular symbol. It has nothing to do with Christianity."

And there's more where that came from.

"It is a fact that Christianity is not a religion. It is a phil-o-so-phy," he told his audience, stretching out the word as if speaking to small children.

Never mind that Webster's New World College Dictionary defines "Christianity" as: (1) Christians collectively; (2) the Christian religion; (3) a particular Christian religious system; (4) the state of being a Christian. No mention of "philosophy."

But in the No-Spin Zone, at least, O'Reilly's facts trump everybody else's as he milks this Christmas controversy, treating this "war" as if it were something new that can be won if he sermonizes loudly enough.

It's nothing new, according to Stephen Nissenbaum, author of "The Battle for Christmas," an absorbing 1996 cultural history of the holiday. Bottom line: The holiness of Christmas has always been challenged by earthly practices. Through the centuries, spirituality and paganism have coexisted at Christmas time uneasily.

"Christmas has been a very difficult holiday to successfully Christianize," said Nissenbaum, a professor emeritus of history at the University of Massachusetts (Amherst). "Christianity has taken over the season, even though in doing so, it has allowed itself to become infused with a lot of non-Christian elements."

Nissenbaum's book reminds us that not until the fourth century did the Church officially decree Dec. 25 as the date for Christmas, because it roughly coincided with the winter solstice, already long observed with a pagan festival.

Leaping ahead to the United States of the 1840s, the holiday had begun to resemble the Christmas we observe today, with the popular poem first published two decades earlier, "'Twas the Night Before Christmas," serving as an influential guidepost. And already — with images of Santa Claus even then being used in advertisements aimed at children — people were decrying the holiday's commercialization.

In short, Christmas has always been in flux and at odds with itself.

Nissenbaum (who during a recent phone interview noted that he was making no references to O'Reilly, whose show he said he's never seen) reflected on the proposition that a Christmas tree is cultural and secular, and therefore shouldn't offend non-Christians.

"That makes real sense only if the people making that argument don't think of Christmas as a religious holiday," he said. "The moment that you see Christmas as a Christian holiday, then something that bears the name 'Christmas' has got to have a religious significance." In other words: You can't have it both ways.

But you can sure try. When it comes to war coverage, O'Reilly spent less than 14 minutes on the wars in Iraq and Afghanistan last December, while devoting roughly 42 minutes to the War on Christmas, according to liberal watchdog group Media Matters for America.

As an "O'Reilly Factor" franchise, the War on Christmas is just the latest chapter in the holiday's contentious history. It makes Christmas a political wedge issue. It's a celebration that, under the pretense of peace and goodwill, is ripe for fighting about on his show.

"Beyond all the controversy lies a much bigger secular progressive agenda," insists O'Reilly, rallying his troops.

Call it what you like, Christmas waged like that is just an annual observance of Us vs. Them.